玉米秸秆和玉米芯生物炭对水溶液中无机氮的吸附性能

The adsorption characters of inorganic nitrogen in aqueous solution by maize straw-and corn cob-derived biochars

为探明玉米秸秆和玉米芯生物炭对水溶液中无机氮的吸附性能,研究了其对NH4＋-N、NO3--N和NO2--N的吸附动力学过程;并用等温吸附模型对NH4＋-N和NO3--N的吸附过程进行拟合,探讨制得生物炭对无机氮的吸附机理.结果表明,400℃和600℃制得玉米秸秆和玉米芯生物炭均呈碱性,表现为400℃〈600℃;同种原材料,与400℃制得生物炭相比,600℃制得生物炭碱性含氧官能团数量较多,而酸性含氧官能团数量较少.400℃制得生物炭对NH4＋-N的吸附能力较强（玉米秸秆和玉米芯生物炭的平衡吸附量分别为4.22和4.09mg/g）;而600℃制得生物炭对NO3--N和NO2--N的吸附能力较强（玉米秸秆和玉米芯生物炭对NO3--N的平衡吸附量分别为0.73和0.63mg/g;对NO2--N的平衡吸附量分别为0.55和0.35mg/g）.与NO3--N和NO2--N相比,玉米秸秆和玉米芯生物炭对NH4＋-N的吸附能力更强,4种生物炭对NH4＋-N的平衡吸附量是NO3--N/NO2--N的4.29~20.2倍.等温吸附模型拟合研究表明,玉米秸秆和玉米芯生物炭对水溶液中NH4＋-N和NO3--N的吸附过程均可用Freundlich模型描述,其在生物炭表面的吸附是多分子层吸附.

In order to explore the adsorption characters of inorganic nitrogen in aqueous solution by maize straw- and corn cob-derived biochars, the adsorption kinetics of NH4＋-N, NO3--N and NO2--N were studied. The adsorption processes of NH4＋-N and NO3--N were fitted by Langmuir and Freundlich isothermal adsorption models, and the adsorption mechanisms were also elucidated. The results showed that the maize straw- and corn cob-derived biochars produced at 400 and 600℃ ℃ were both alkaline（400℃600℃）. As for the same raw material, the biochar produced at 600℃ showed relatively higher alkaline oxygen-containing functional group content and lower acidic oxygen-containing functional group content compared with the biochar produced at 400℃. The biochars produced at 400℃ had a stronger adsorption capacity to NH4＋-N（the equilibrium adsorption amounts of maize straw- and corn cob-derived biochars were 4.22 and 4.09mg/g, respectively）. However, the biochars produced at 600℃ had a stronger adsorption capacity to NO3--N and NO2--N（for NO3--N： the equilibrium adsorption amounts of maize straw- and corn cob-derived biochars were 0.73 and 0.63mg/g, respectively; for NO2--N： 0.55 and 0.35mg/g, respectively）. Compared to NO3--N and NO2--N, all the four kinds of biochar showed stronger adsorption capacity to NH4＋-N, and the equilibrium adsorption amounts of NH4＋-N were 4.29~20.2 times more than NO3--N/NO2--N. The isothermal adsorption model study showed that the adsorption of NH4＋-N and NO3--N in aqueous solution by maize straw- and corn cob-derived biochars could be described by Freundlich model, and the multi-layer adsorption was the major adsorption mechanism.